Retention behavior of dilute polymers

This study investigates the retention behavior of dilute polymer solutions in oil sands. Results indicate that the presence of a large amount of fines and/or a variety of minerals in the sand may result in high adsorption and retention causing excessive loss of polymer and high injection pressures. Injection of a surfactant with the polymer leads to increased oil recoveries because the dilute polymer may selectively adsorb on mineral grain surfaces leaving the surfactant to act at liquid/iiquid contacts. 

KIKANI AND SOMERTON Retention Behavior of Dilute Polymers... 

The principles of IGC, as a gas-phase technique used to characterize the surface and bulk properties of solid materials, are very simple as the process is the reverse of conventional gas chromatography. Typically, an empty cylindrical column is uniformly packed with the solid material of interest, normally a powder, fiber, or film. A pulse or constant concentration of gas is then injected down the column at a fixed carrier gas flow rate, and the retention behavior of the pulse or concentration front is measured with a detector (Figure 10.1). The retention of a solvent or probe molecule on the material is recorded and the measurement is made effectively at an inflnite dilution of the probe. A range of thermodynamic parameters can then be calculated. A major advantage of IGC is that it is readily applicable to mixtures of two or more polymers. 

For infinite dilution operation the carrier gas flows directly to the column which is inserted into a thermostated oil bath (to get a more precise temperature control than in a conventional GLC oven). The output of the column is measured with a flame ionization detector or alternately with a thermal conductivity detector. Helium is used today as carrier gas (nitrogen in earlier work). From the difference between the retention time of the injected solvent sample and the retention time of a non-interacting gas (marker gas), the thermodynamic equilibrium behavior can be obtained (equations see below). Most experiments were made up to now with packed columns, but capillary columns were used, too. The experimental conditions must be chosen so that real thermodynamic data can be obtained, i.e., equilibrium bulk absorption conditions. Errors caused by unsuitable gas flow rates, unsuitable polymer loading percentages on the solid support material and support surface effects as well as any interactions between the injected sample and the solid support in packed columns, unsuitable sample size of the injected probes, carrier gas effects, and imprecise knowledge of the real amount of polymer in the column, can be sources of problems, whether data are nominally measured under real thermodynamic equilibrium conditions or not, and have to be eliminated. The sizeable pressure drop through the column must be measured and accounted for. 

---